The feeding of single large sheets of corrugated paperboard to rotary slotters is conventionally accomplished utilizing substantial manual manipulations in order to control and regulate the supply of the sheets, and the position of same, on the feed chain which supplies the individual sheets to the rollers. This manual operation has generally been utilized in view of the difficulty in removing single sheets of semi-rigid corrugated paperboard from the stack, and then successfully handling and transferring same to the slotter. However, these manual manipulations are obviously time and labor consuming, so that the overall operation is hence extremely inefficient and expensive. Thus, the cutting, slitting or printing of sheets using this technique has long been recognized as inefficient and expensive, but nevertheless has been utilized in many instances in view of the unavailability of relatively inexpensive and efficient equipment capable of performing these steps automatically.
While some rotary slotters, particularly printertype slotters, have utilized high speed automatic reciprocating-type feed mechanisms for supplying individual sheets from a stack to the slotter, nevertheless these known devices are of extreme mechanical complexity so as to make their maintenance and repair extremely difficult, and these devices are also initially of great expense. For this reason, these devices have been considered wholly unsuitable by many operators of rotary slotters, and particularly those operators who utilize their equipment on a much smaller scale.
In an attempt to provide such an automatic sheet feeding device for a rotary slotter, and specifically a device of lesser cost and complexity so as to be suitable for operations of smaller scale, there has been developed the sheet pick-up and feeder device illustrated by U.S. Pat. No. 4,003,567. With this device, however, the pick-up and transfer of the individual sheets requires the use of a reciprocating suction mechanism which is mounted on and controlled by a linkage which interconnects same to an endless chain so that the overall mechanism including the suction members hence undergoes a rather complex cycle movement, whereby the resulting mechanism is both complex and the rate of feeding sheets is slower than desired, and is restricted with respect to the capability of being adjusted so as to handle sheets having a substantial range of widths. Also, this apparatus is driven from the slotter and hence requires complex drive trains.
Accordingly, the present invention relates to an improved apparatus for handling stacks of sheets, particularly sheets of semi-rigid material such as corrugated paperboard, and for permitting a single sheet to be picked up and movably advanced for supply to a further processing apparatus, specifically a rotary slotter.
In the improved apparatus, there is provided an elevator for receiving thereon a stack of sheets. The elevator is of an open framework so that a plurality of belt conveyors are positioned within the open framework of the elevator, which belt conveyors are aligned with additional conveyors positioned adjacent but spaced sidewardly of the elevator. A stack of sheets can be automatically conveyed from these side conveyors onto the belt conveyors, when the elevator is in its lowered position, whereby the belt conveyors move the stack into position against a support plate. The elevator is raised to lift the stack away from the belt conveyors, which lifting is controlled by a sensor, such as a photocell, which maintains the top of the stack within a selected vertical range so that a small number of individual sheets can be removed, following which the elevator will be automatically lifted so that the top of the stack is always maintained within a selected range of positions. A pick-up and advancing mechanism is disposed above the elevator for lifting the rear edge of the top sheet and then slidably advancing the sheet forwardly between pairs of nip rollers, the lowermost nip rollers being associated with a set of downwardly inclined conveyor belts which then feed the separated sheet onto the chain conveyor associated with the rotary slotter.
In this apparatus, the pick-up and advancing mechanism employs a primary carriage assembly which is supported for horizontal linear movement in the widthwise direction of the stacked sheets, which main carriage is activated when the stack is positioned on the elevator so that appropriate positioning elements are disposed directly adjacent one side edge of the stack, thereby permitting adjustment for sheets of different size. This main carriage also mounts thereon a row of vertically movable suction devices which engage the top sheet adjacent the trailing edge thereof for permitting this trailing edge to be lifted upwardly a selected extent. A secondary carriage is supported on the primary carriage for linear reciprocating movement in the same direction, which secondary carriage mounts thereon a row of pushing elements which include fingers which are adapted to move into position below the raised rear edge of the sheet for supporting the rear edge in a raised position when the suction members release the sheet. This secondary carriage and the pushing elements thereon are advanced widthwise across the stack so as to push the leading edge of the top sheet into the nip rollers. When the secondary carriage reaches its forward stroke position, an appropriate control reverses the secondary carriage and causes it to automatically return to its initial retracted position, and simultaneously therewith the suction devices are again energized to create a suction therein and are moved downwardly to both engage the next top sheet and are then moved upwardly to raise the rear edge of this next top sheet so that same is in a raised position simultaneous with the return of the secondary carriage to its retracted position, whereby the apparatus is in position to initiate a further cycle. Each cycle of the pick-up and advancing mechanism is initiated by a limit switch associated with the drive chain of the rotary slotter, which sensor initiates a new cycle whenever the previously-removed sheet reaches a preselected position on the chain feeder of the slotter.
It is an object of the improved apparatus, as described above, to permit single sheets to be rapidly and efficiently removed from a stack and fed to the chain feeder of a rotary slotter, with the feeding of the single sheet from the stack to the rotary slotter being controlled by and synchronized with the feed chain of the slotter to permit the overall operation to be carried out at a rapid rate and in a substantially wholly automated manner so as to provide optimum efficiency while requiring minimum manual supervision and control.
A further object of the invention is to provide an improved apparatus, as aforesaid, which is of minimal mechanical complexity so as to provide optimum reliability and efficiency, and at the same time enable the apparatus to be manufactured and operated with minimal expense.
A still further object is to provide an improved apparatus, as aforesaid, which is provided with its own motors and drive mechanisms so as to minimize or eliminate driving connections from the rotary slotter, with the drives and cyclic actuation of the apparatus being controlled by a signal received from the rotary slotter in dependence on the positioning of a sheet thereon, whereby the apparatus can be utilized in association with conventional rotary slotters without having to substantially modify or rebuild the drive train thereof.
Another object is to provide an improved apparatus, as aforesaid, which utilizes a pneumatic system for controlling many of the essential mechanisms and devices, such as the suction elements and the movement of the secondary carriage, so as to simplify the overall mechanical complexity of the apparatus. This improved apparatus also facilitates the supplying of stacks of sheets thereto so as to simplify this operation and permit it to be accomplished more automatically, and at the same time this apparatus utilizes an improved elevator mechanism combined with a supply conveyor so as to facilitate the overall transfer and handling of stacks of sheets.
Other objects and purposes of the invention will be apparent to persons familiar with systems of this general type upon reading the following specification and inspecting the accompanying drawings.